Most forms of cognition actually involve multiple cognitive functions working in unison, however tests can be organised into broad categories based on the cognitive function which they predominantly assess. Some tests appear under multiple headings as different versions and aspects of tests can be used to assess different functions.
Intelligence testing in a research context is relatively more straightforward than in a clinical context. In research, intelligence is tested and results are generally as obtained, however in a clinical setting intelligence may be impaired so estimates are required for comparison with obtained results. Premorbid estimates can be determined through a number of methods, the most common include: comparison of test results to expected achievement levels based on prior education and occupation and the use of hold tests which are based on cognitive faculties which are generally good indicators of intelligence and thought to be more resistant to cognitive damage, e.g. language.
Memory is a very broad function which includes several distinct abilities, all of which can be selectively impaired and require individual testing. There is disagreement as to the number of memory systems, depending on the psychological perspective taken. From a clinical perspective, a view of five distinct types of memory, is in most cases sufficient. Semantic memory and episodic memory (collectively called declarative memory or explicit memory); procedural memory and primingor perceptual learning (collectively called non-declarative memory or implicit memory) all four of which are long term memory systems; and working memory or short term memory. Semantic memory is memory for facts, episodic memory is autobiographical memory, procedural memory is memory for the performance of skills, priming is memory facilitated by prior exposure to a stimulus and working memory is a form of short term memory for information manipulation.
Language functions include speech, reading and writing, all of which can be selectively impaired.
Executive functions is an umbrella term for a various cognitive processes and sub-processes. The executive functions include: problem solving, planning, organizational skills, selective attention, inhibitory control and some aspects of short term memory.
Neuropsychological tests of visuospatial functionshould cover the areas of visual perception, visual construction and visual integration. Though not their only functions, these tasks are to a large degree carried out by areas of the parietal lobe.
Dementia testing is often done by way of testing the cognitive functions that are most often impaired by the disease e.g. memory, orientation, language and problem solving. Tests such as these are by no means conclusive of deficits, but may give a good indication as to the presence or severity of dementia.
Batteries assessing multiple neuropsychological functions
There are some test batteries which combine a range of tests to provide an overview of cognitive skills. These are usually good early tests to rule out problems in certain functions and provide an indication of functions which may need to be tested more specifically.
The most beneficial factor of neuropsychological assessment is that it provides an accurate diagnosis of the disorder for the patient when it is unclear to the psychologist what exactly he/she has. This allows for accurate treatment later on in the process because treatment is driven by the exact symptoms of the disorder and how a specific patient may react to different treatments. The assessment allows the psychologist and patient to understand the severity of the deficit and to allow better decision-making by both parties. It is also helpful in understanding deteriorating diseases because the patient can be assessed multiple times to see how the disorder is progressing.